Phosphorylation Levels Of AMPK Research Articles

Magnolol protects pancreatic β-cells against methylglyoxal-induced cellular dysfunction

Chronic hyperglycemia aggravates insulin resistance, in part due to increased formation of advanced glycation end-products (AGEs). Methylglyoxal (MG), a major precursor of AGEs, accumulates abnormally in various tissues and organs and participates in oxidative damage. We investigated the insulinotropic benefits of magnolol, a hydroxylated biphenyl compound isolated from Magnolia officinalis, in pancreatic β-cells exposed to MG in vitro. When exposed to cytotoxic levels of MG for 48 h, RIN-m5F β-cells exhibited a significant loss of viability and impaired insulin secretion, whereas pretreatment with magnolol protected against MG-induced cell death and decreased insulin secretion. Moreover, magnolol increased the expression of genes involved in β-cell survival and function, including Ins2 and PDX1. Furthermore, magnolol increased the levels of AMPK phosphorylation, SIRT1, and PGC1α in RIN-5F β-cells. In addition, magnolol increased the activity of glyoxalase I and decreased the levels of MG-modified protein adducts, which suggests that magnolol protects against MG-induced protein glycation. Taken together, the results indicate the potential application of magnolol as an intervention against MG-induced hyperglycemia.

Curcumin administration suppresses collagen synthesis in the hearts of rats with experimental diabetes.

Cardiac fibrosis is considered the initial change of diabetic cardiomyopathy (DCM). We have shown that curcumin alleviates collagen deposition in DCM, but the mechanism remains unknown. In this study we sought to investigate the effects of curcumin on cardiac fibrosis in vivo and in vitro and to elucidate the underlying mechanisms. Experimental diabetes was induced in rats by injection of low-dose streptozotocin (STZ) combined with high energy diet. The rats were orally treated with curcumin (300 mg·kg-1·d-1) for 16 weeks. Curcumin administration significantly suppressed the deposition of type I and type III collagens in the heart tissues of diabetic rats, accompanied by markedly reduced TGF-β1 production, suppressed TβR II levels and Smad2/3 phosphorylation, and increased Smad7 expression. Similar effects were observed in human cardiac fibroblasts exposed to high glucose (HG, 30 mmol/L) or exogenous TGF-β1 (5 ng/mL). Furthermore, TGF-β1 or HG treatment significantly increased the phosphorylation levels of AMPK and p38 MAPK in the fibroblasts. Application of curcumin (25 μmol/L) inhibited TGF-β1- or HG-induced AMPK/p38 MAPK activation and suppressed collagen synthesis in the fibroblasts. These effects were similar to those of the AMPK inhibitor compound C (10 μmol/L) but opposite to the effects of the AMPK activator metformin (2 mmol/L) in the fibroblasts. Our results demonstrate that curcumin suppresses diabetes-associated collagen synthesis in rat myocardium not only by inhibiting TGF-β1 production and canonical Smad signaling but also by blocking the non-canonical AMPK/p38 MAPK pathway.

Lactoferrin promotes autophagy via AMP-activated protein kinase activation through low-density lipoprotein receptor-related protein 1

Lactoferrin (LF) is a multifunctional, iron-binding glycoprotein in mammalian secretions, such as breast milk, and has several beneficial effects for human health. However, how these effects are exerted at the cellular level is still largely unknown. In this study, we investigated the effects of LF on autophagy activity in NIH/3T3 mouse fibroblasts. LF from bovine milk was found to increase LC3-I to LC3-II conversion and LC3-positive cytosolic punctate structures because of increased autophagy flux. Knockdown of the putative LF receptor low-density receptor-related protein 1 (LRP1) completely abolished LC3 conversion in cells by LF treatment. Moreover, exposure to LF increased the phosphorylation levels of AMPK in cells, and treatment of dorsomorphin, a pharmacological inhibitor of AMPK signaling, attenuated LC3 conversion by LF. Therefore, we concluded that the beneficial effects of LF might be due to an increase of autophagy activity via AMPK signaling through the LRP1 receptor. These findings provide a novel insight into the physiological role of LF for the maintenance of cellular and tissue homeostasis.

5-ALA ameliorates hepatic steatosis through AMPK signaling pathway.

5-Aminolevulinic acid (5-ALA), the first compound in the porphyrin synthesis pathway, has been reported to ameliorate the diabetic state in Otsuka Long-Evans Tokushima Fatty rats by reducing fat pad weight in the retroperitoneal region. Dietary supplementation with 5-ALA has additionally demonstrated the capacity to lower blood glucose and HbA1c levels among subjects with diabetes. The etiology of nonalcoholic fatty liver disease (NAFLD) is complex and its typical characteristics include obesity and insulin resistance. As 5-ALA supplementation has previously normalized glucose and insulin resistance, we sought to investigate whether 5-ALA had potential therapeutic effects on NAFLD and elucidate the signal pathway mediating these effects. To explore these questions, we fed C57BL/6J mice a high-fat diet (HFD) to induce a fatty liver disease and supplemented the diet-induced obese (DIO) mice with 5-ALA. The mice in the presence of 5-ALA demonstrated a decrease in body weight and hepatic lipid content and moderate improvement in glucose homeostasis compared to untreated controls. Further, we found that 5-ALA activated AMPK signaling pathway, which was correlated with enhanced lipolysis and fatty acid β-oxidation. Human hepatocarcinoma cells (HepG2 cells) treated with 5-ALA were additionally used to investigate the mechanics of 5-ALA. Treated cells had a higher expression of lipolysis-related genes, including PGC-1α. Our data indicated that 5-ALA might represent a novel compound that could be useful for the treatment of nonalcoholic fatty liver disease (NAFLD), likely through the restoration of phosphorylation levels of AMPK (Thr172) and acetyl-CoA (ACC) (Ser79), further enhanced PGC1α and CPT1α expression.

Nitric oxide synthesis-promoting effects of valsartan in human umbilical vein endothelial cells via the Akt/adenosine monophosphate-activated protein kinase/endothelial nitric oxide synthase pathway.

Valsartan (VAL), an antagonist of angiotensin II receptor type 1, has antihypertensive and multiple cardiovascular protective effects. The pleiotropic functions of VAL are related to the increased synthesis and biological activity of intravascular nitric oxide (NO). In this study, the role and mechanisms of VAL in the synthesis of NO were examined in human umbilical vein endothelial cells (HUVECs). Ten µmol/L of VAL was used to treat EA.hy926 cells for 30 minutes, 1, 3, 6, 12, and 24 hours, and three concentrations of VAL (i.e., 10, 1, and 0.1 µmol/L) were used to treat EA.hy926 cells for 24 hours. The cells were divided into five groups: control, VAL, VAL + Compound C (adenosine monophosphate-activated protein kinase [AMPK] inhibitor, 1 µmol/L), VAL + LY294002 (Akt [protein kinase B] inhibitor, 10 µmol/L), and VAL + L-nitro-arginine methyl ester (L-NAME, endothelial NO synthase [eNOS] inhibitor, 500 µmol/L) groups. The NO content in the VAL-treated HUVEC line (EA.hy926) was detected using the nitrate reductase method, and western blot was used to detect the phosphorylation of Akt, AMPK, and eNOS, as well as the changes in total protein levels. VAL increased NO synthesis in EA.hy926 cells in time- and dose-dependent manners (p < 0.05) and the intracellular phosphorylation levels of Akt, AMPK, and eNOS at the corresponding time points. LY294002, Compound C, and L-NAME could inhibit the VAL-promoted NO synthesis. VAL activated Akt, AMPK, and eNOS, thus promoting NO synthesis and playing a protective role in endothelial cells. These results partially explained the mechanisms underlying the cardiovascular protective effects of VAL.

Phellinus linteus Mycelium Alleviates Myocardial Ischemia-Reperfusion Injury through Autophagic Regulation.

The incidence of myocardial ischemia-reperfusion (IR) injury is rapidly increasing around the world and this disease is a major contributor to global morbidity and mortality. It is known that regulation of programmed cell death including apoptosis and autophagy reduces the impact of myocardial IR injury. In this study, the cardioprotective effects and underlying mechanisms of Phellinus linteus (Berk. and Curt.) Teng, Hymenochaetaceae (PL), a type of medicinal mushroom, were examined in rats subjected to myocardial IR injury. The left main coronary artery of rats was ligated for 1 h and reperfused for 3 h. The arrhythmia levels were monitored during the entire process and the infarct size was evaluated after myocardial IR injury. Furthermore, the expression levels of proteins in apoptotic and autophagic pathways were observed. Pretreatment with PL mycelium (PLM) significantly reduced ventricular arrhythmia and mortality due to myocardial IR injury. PLM also significantly decreased myocardial infarct size and plasma lactate dehydrogenase level after myocardial IR injury. Moreover, PLM administration resulted in decreased caspase 3 and caspase 9 activation and increased Bcl-2/Bax ratio. Phosphorylation level of AMPK was elevated while mTOR level was reduced. Becline-1 and p62 levels decreased. These findings suggest that PLM is effective in protecting the myocardium against IR injury. The mechanism involves mediation through suppressed pro-apoptotic signaling and regulation of autophagic signaling, including stimulation of AMPK-dependent pathway and inhibition of beclin-1-dependent pathway, resulting in enhancement of protective autophagy and inhibition of excessive autophagy.

Effects of tiletamine on the adenosine monophosphate-activated protein kinase signaling pathway in the rat central nervous system

ObjectiveThe dissociative anesthetic tiletamine, which acts on the central nervous system (CNS), is widely used in veterinary medicine and animal experiments. Recent studies indicate that adenosine 5′-monophosphate activated protein kinase (AMPK) plays a key role in the analgesic action of tiletamine. In the present study, the effects of tiletamine on the AMPK signaling pathway in rats were investigated. MethodsSprague-Dawley rats were injected intraperitoneally with tiletamine and executed at 10, 20, 40 and 60min post injection. The cerebral cortex, hippocampus, thalamus, cerebellum and brainstem were immediately taken out to evaluate the mRNA and protein phosphorylation levels of liver kinase B1 (LKB1), AMPKα and eIF4E-binding protein 1 (4EBP1) using quantitative real-time polymerase chain reaction and western blot analysis. ResultsTiletamine increased AMPK mRNA expression in the rat brain (P<0.01). Increased mRNA expression of AMPK was accompanied by an increase in phosphorylation of LKB1, resulting in significant decreases in the phosphorylation levels of 4EBP1 in the corresponding brain regions (P<0.01). ConclusionIn summary, the findings indicate that tiletamine regulates the mRNA expression and protein phosphorylation levels of LKB1, AMPK and 4EBP1 in the CNS, suggesting that the analgesic effect of the anesthetic is mediated, at least in part, by the AMPK signaling pathway.

Long-term resistance exercise-induced muscular hypertrophy is associated with autophagy modulation in rats.

Elevation of anabolism and concurrent suppression of catabolism are critical metabolic adaptations for muscular hypertrophy in response to resistance exercise (RE). Here, we investigated if RE-induced muscular hypertrophy is acquired by modulating a critical catabolic process autophagy. Male Wistar Hannover rats (14weeks old) were randomly assigned to either sedentary control (SC, n=10) or resistance exercise (RE, n=10). RE elicited significant hypertrophy of flexor digitorum profundus (FDP) muscles in parallel with enhancement in anabolic signaling pathways (phosphorylation of AKT, mTOR, and p70S6K). Importantly, RE-treated FDP muscle exhibited a significant decline in autophagy evidenced by diminished phosphorylation levels of AMPK, a decrease in LC3-II/LC3-I ratio, an increase in p62 level, and a decline in active form of lysosomal protease CATHEPSIN L in the absence of alterations of key autophagy proteins: ULK1 phosphorylation, BECLIN1, and BNIP3. Our study suggests that RE-induced hypertrophy is achieved by potentiating anabolism and restricting autophagy-induced catabolism.

Effect of combined aerobic and strength exercises on the regulation of mitochondrial biogenesis and protein synthesis and degradation in human skeletal muscle

We tested the hypothesis that strength exercise after intermittent aerobice exercise might activate signalling pathways related to mitochondrial biogenesis (phosphorylation level of AMPK, p38; expression of PGC-1a, NT-PGC-la, TFAM, VEGFA), to protein synthesis (phosphorylation level of p70S6Kl(Thr389) eEF2(Thr56) expression of IGF-lEa, IGF-lEc (MGF), REDDl) and to proteolysis (phosphorylation level of FOXOl(Ser256) and expression of MURFl, MAFbx, Myostatin) in trained skeletal muscle. Nine amateur endurance-trained athletes performed 70-Min bicycle intermittent exercise with both legs (E), followed by one-leg strength exercise (ES: 4 bouts of knee extensions at 75% MVC till exhaustion). Gene expression and protein level were evaluated in samples from m. vastus lateralis before, 40 min, 5 and 22 h after the aerobic exercise. The phosphorylation level of the ACC(Ser79/222)(an endogenous marker of AMPK activity) and expression of PGC-la-related TFAM - marker of mitochondrial biogenesis were increased after E exercise and did not changed after ES. Expression of PGC-lα and truncated isoform NT- PGC-lα was increased in both legs as well. Insulin concentration in blood was dramatically, 7.5-fold diminished after intermittent aerobic exercise. Phosphorylation of FOXO(Ser256) - regulator of ubiquitin-related proteolysis - was decreased after both E and ES exercise, it means it was activated in both cases, while expression of E3-ubiquitin ligase MURFl was increased only after E exercise. Both aerobic and combined exercise did not affect regulation of protein synthesis: neither expression of IGF-lEa and IGF-Ec (MGF) mRNA isoforms nor phosphorylation levels of markers of protein synthesis p70S6Kl(Thr389) and eEF2(Thr56) were changed. Thus effects of aerobic exercise in trained muscles are noticeably suppressed by performing strength exercise immediately after endurance one. In particular, the activity of signalling cascades and expression of genes regulating mitochondrial biogenesis are lessened, but protein synthesis regulation is not affected. And at last strength exercise suppresses induced by aerobic exercise expression of MURF1 gene - marker of ubiquitin proteasome system. It means that strength exercise just after intermittent aerobic exercise might have a negative effect on aerobic performance if used chronically.

Anti-neuroinflammatory Effect of Emodin in LPS-Stimulated Microglia: Involvement of AMPK/Nrf2 Activation.

AMPK/Nrf2 signaling regulates multiple antioxidative factors and exerts neuroprotective effects. Emodin is one of the main bioactive components extracted from Polygonum multiflorum, a plant possessing important activities for human health and for treating a variety of diseases. This study examined whether emodin can activate AMPK/Nrf2 signaling and induce the expression of genes targeted by this pathway. In addition, the anti-neuroinflammatory properties of emodin in lipopolysaccharide (LPS)-stimulated microglia were examined. In microglia, the emodin treatment increased the levels of LKB1, CaMKII, and AMPK phosphorylation. Emodin increased the translocation and transactivity of Nrf2 and enhanced the levels of HO-1 and NQO1. In addition, the emodin-mediated expression of HO-1 and NQO1 was attenuated completely by an AMPK inhibitor (compound C). Moreover, emodin decreased dramatically the LPS-induced production of NO and PGE2 as well as the protein expression and promoter activity of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, emodin effectively inhibited the production of pro-inflammatory cytokines, TNF-α and IL-6, and reduced the level of IκBα phosphorylation, leading to the suppression of the nuclear translocation, phosphorylation, and transactivity of NF-κB. Emodin also suppressed the LPS-stimulated activation of STATs, JNK, and p38 MAPK. The anti-inflammatory effects of emodin were reversed by transfection with Nrf-2 and HO-1 siRNA and by a co-treatment with an AMPK inhibitor. These results suggest that emodin isolated from P. multiflorum can be used as a natural anti-neuroinflammatory agent that exerts its effects by inducing HO-1 and NQO1 via AMPK/Nrf2 signaling in microglia.

Abstract 313: Nonionic Acid is a Target Metabolite of Diabetic Microvasculopathy

Aim: The purpose of this study is to screen the target metabolites of diabetic microangiopathy in heart by use of whole heart metabolome analysis. Methods: Diet-induced type 2 diabetic mouse were divided into two groups; control and those treated with diabetic remedy GLP-1 receptor agonist Ex-4 for 5 weeks. Mice were euthanized and analyzed at the age of 16 week-old. Results: The capillary density of the T2DM was reduced as compared to those non-diabetic counterparts, which was restored by Ex4 treatment. Changes in angiogenic signals detected by immunoblotting analysis revealed that the phosphorylation levels of eNOS and AMPK were elevated by Ex-4, but those Akt remained unchanged. Tube formation assay revealed that Ex-4 increased tube length and branch points in HUVECs. Consistently with the trend that was observed in vivo experiment, AMPK and eNOS phosphorylation levels were enhanced by Ex4 without affecting Akt phosphorylation. To screen the candidate metabolites that is responsible for the diabetic microvasculopathy in GLP-1-dependent fashion, we performed metabolome analysis by using the whole heart of each mouse. The hierarchical cluster analysis revealed that nonanoic acid (NNA) was the only metabolite that increased in type 2 diabetic mice with concomitant decline by Ex-4 treatment. We next examined the impact of nonanoic acid on in vitro angiogenesis and found that NNA suppressed tube length and branch points in HUVECs in a dose-dependent fashion. Interestingly, NNA canceled eNOS and AMPK phosphorylation that was enhanced by Ex4. Conclusion: GLP-1 ameliorated diabetic microvasculopathy via the AMPK and eNOS axis. NNA is presumably one of the novel anti-angiogenic metabolites that causes diabetic microangiopathy.

Antidiabetic activity of perylenequinonoid-rich extract from Shiraia bambusicola in KK-Ay mice with spontaneous type 2 diabetes mellitus

Ethnopharmacological relevanceBitter and cold traditional Chinese medicines (TCMs) have been long used to treat diabetes mellitus (DM) based on unique medical theory system since ancient China. As one of bitter and cold TCMs, the stromatas of Shiraia bambusicola have been used for the treatment of DM and exerted clinical effects to a certain extent. However, the corresponding active principles and antidiabetic mechanism of the TCM still remain unknown. Therefore, the aim of the present investigation was to evaluate the potential antidiabetic effect of the active Shiraia bambusicola EtOAc extract (SB-EtOAc) in vitro and in vivo, and elucidate its probable antidiabetic mechanism. Materials and methodsA LC-PDA-ESIMS protocol was developed to determine the chemical principles of the active EtOAc extract rapidly and unambiguously. The effect of SB-EtOAc on the glucose transporter type 4 (GLUT4) translocation and glucose uptake in L6 cells was examined. SB-EtOAc was orally administration at the dose of 30, 60 and 120mg/kg/d in KK-Ay mice, for 21 days. Body weight, plasma glucose, oral glucose tolerance test, fasted blood glucose levels, oral glucose tolerance test and insulin tolerance test, serum insulin and blood–lipid indexes were measured. GLUT4 on L6 cells membrane and phosphorylation of the AMP-activated protein kinase (p-AMPK) expression in L6 cells were measured. The GLUT4 and p-AMPK expression in KK-Ay mice skeletal muscle were measured. Phosphorylation of the acetyl-CoA carboxylase (p-ACC) and p-AMPK were measured. ResultsIn vitro, SB-EtOAc exhibited a strong effect of stimulation on GLUT4 translocation by 3.2 fold in L6 cells compared with basal group, however, the selective AMPK inhibitor compound C can completely inhibit the AMPK pathway and prevent the GLUT4 translocation caused by SB-EtOAc. The further western blotting experiments showed that SB-EtOAc can stimulate AMPK phosphorylation in L6 cells and improve the expression of GLUT4. In vivo, SB-EtOAc can improve the KK-Ay mice insulin resistant and oral glucose tolerance to a certain extent. And the body weight, blood glucose levels and the serum TC, TG, FFA, AST, ALT and LDL-C were significantly reduced and HDL-C were increased after 3 weeks treatment. Mechanistically, phosphorylation of the AMPK and ACC had been improved obviously and the levels of AMPK phosphorylation and GLUT4 had been also enhanced. ConclusionIn vitro, SB-EtOAc exhibited a strong effect of stimulation on GLUT4 translocation and improved significantly the glucose uptake. In vivo, SB-EtOAc significantly improved oral glucose tolerance and the insulin resistant as well as glucolipid metabolism. In this study, SB-EtOAc displayed promising positive antidiabetic activity in vitro and in vivo, partly by modulating AMPK-GLUT4 and AMPK-ACC signaling pathways.

Mitochondria related peptide MOTS-c suppresses ovariectomy-induced bone loss via AMPK activation

Therapeutic targeting bone loss has been the focus of the study in osteoporosis. The present study is intended to evaluate whether MOTS-c, a novel mitochondria related 16 aa peptide, can protect mice from ovariectomy-induced osteoporosis. After ovary removal, the mice were injected with MOTS-c at a dose of 5 mg/kg once a day for 12 weeks. Our results showed that MOTS-c treatment significantly alleviated bone loss, as determined by micro-CT examination. Mechanistically, we found that the receptor activator of nuclear factor-κB ligand (RANKL) induced osteoclast differentiation was remarkably inhibited by MOTS-c. Moreover, MOTS-c increased phosphorylated AMPK levels, and compound C, an AMPK inhibitor, could partially abrogate the effects of the MOTS-c on osteoclastogenesis. Thus, our findings provide evidence that MOTS-c may exert as an inhibitor of osteoporosis via AMPK dependent inhibition of osteoclastogenesis.

Gamma Tocotrienol Suppresses NLRP3 Inflammasome by Dual Mechanism of A20‐ mediated Priming Inhibition and AMPK/autophagy Axis Activation

Nod‐like receptor 3 (NLRP3) inflammasome is the intracellular innate immunity sensor that processes and releases IL‐1β in response to microbial invasion or metabolic danger signals such as saturated fatty acids and free cholesterol. Aberrant activation of NLRP3 is intimately associated with numerous chronic inflammatory diseases. However, little information is available as to whether NLRP3 inflammasome is regulated by dietary factors. The aim of this study is to investigate whether gamma‐tocotrienol (γT3), an unsaturated form of vitamin E, downregulates NLRP3 inflammasome activation, and to determine the molecular mechanisms. Pretreatment of γT3 (0.5–10 mM) significantly suppressed activation of NLRP3 inflammasome reporter, caspase‐1 cleavage, and IL‐1β and IL‐18 secretion in J774 macrophages as well as bone marrow‐derived murine macrophages (BMDM). To further determine the mechanisms, we investigate the role of γT3 on NFκB activation and AMPK/autophagy axis activation. γT3 significantly attenuated proinflammatory gene expressions of IL‐1β, IL‐18 and NLRP3, and induced A20 expression, an ubiquitin‐editing enzyme to interrupt NFκB signaling. Induction of A20 concurred with 1) the decrease of p‐IKKα/β, p‐ERK, and p‐IκBα; 2) the reappearance of IκBα, and 3) the disappearance of TRAF6, suggesting a negative feedback of A20 on TRAF6/IKK/NF‐κB signaling. Moreover, silencing of A20 markedly dampened the inflammasome inhibitory effects of γT3. Intriguingly, γT3 treatment was also associated with AMPK/autophagy axis activation shown through LC3II accumulation and increased levels of AMPK phosphorylation. The inhibition of AMPK with Compound C completely reversed γT3's inhibitory role on NLRP3 inflammasome and caspase‐1 cleavage. Taken together, we demonstrated that γT3 suppresses NLRP3 inflammasome by two mechanisms, 1) inhibition of TRAF6/NFκB axis activation through induction of A20, and 2) activation of AMP kinase/autophagy thereby inhibiting inflammasome assembly.Support or Funding InformationAmerican Heart Association

Cilostazol Suppresses IL-23 Production in Human Dendritic Cells via an AMPK-Dependent Pathway

Background/Aims: Cilostazol has been previously demonstrated to inhibit IL-23 production in human synovial macrophages via a RhoA/ROCK-dependent pathway. However, whether cilostazol affects IL-23 production in human dendritic cells remains largely unknown. The present study was designed to investigate this question and elucidate the possible underlying mechanisms. Methods: Human monocyte-derived dendritic cells (mo-DCs) were pretreated with or without cilostazol and then incubated with zymosan. Enzyme-linked immunosorbent assay (ELISA) and real time PCR analyses were used to measure IL-23 protein expression and RNA levels, respectively, whereas Western blotting was used to measure the expression and phosphorylation level of AMPK. Results: Our results demonstrated that cilostazol suppressed zymosan-induced IL-23 protein production in a concentration dependent manner without affecting dendritic cell viability. In addition, it was found that cilostazol suppressed the expression of the p19 and p40 subunits of IL-23. Moreover, cilostazol mimicked the effect of the AMPK agonist A-769662, as demonstrated by the fact that IL-23 production was also inhibited by A-769662, and the effect of cilostazol on IL-23 production was blocked by the AMPK antagonist Compound C. More importantly, Western blotting demonstrated that cilostazol led to an increased phosphorylation of AMPK. Conclusion: Collectively, our data suggest that cilostazol inhibits the production of IL-23 in human mo-DCs, potentially via the activation of AMPK. This suggests that cilostazol could be an effective anti-inflammatory agent in IL-23- and dendritic cell-related diseases.

Antidiabetic and Antihyperlipidemic Properties of a Triterpenoid Compound, Dehydroeburicoic Acid, from Antrodia camphorata in Vitro and in Streptozotocin-Induced Mice.

The aim of this study was to examine the effects of dehydroeburicoic acid (TT) on type 1 diabetes mellitus and dyslipidemia in streptozotocin (STZ)-induced diabetic mice. STZ-induced diabetic mice were randomly divided into six groups and given orally by gavage TT (at three dosages), metformin (Metf), fenfibrate (Feno), or vehicle for 4 weeks. STZ-induced diabetic mice showed elevations in blood glucose levels (P < 0.001). TT treatment markedly decreased blood glucose levels by 42.6-46.5%. Moreover, STZ-induced diabetic mice displayed an increase in circulating triglyceride (TG) and total cholesterol (TC) levels (P < 0.001 and P < 0.01, respectively) but a decrease in blood insulin and adiponectin levels (P < 0.01 and P < 0.05, respectively). These substances are also reversed by TT treatment, indicating TT ameliorated diabetes and dyslipidemia. Membrane skeletal muscular expression levels of glucose transporter 4 (GLUT4) and expression levels of AMPK phosphorylation (phospho-AMPK) in both liver and skeletal muscle were reduced in STZ-induced diabetic mice, which normalized upon TT treatment and correction of hyperglycemia accompanied with a decrease in mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6 Pase), which was related to the inhibition of hepatic glucose production and attenuating diabetic state. In addition, TT also showed hypolipidemic effect by increasing hepatic expression levels of peroxisome proliferator-activated receptor α (PPARα) and mRNA levels of carnitine palmitoyl transferase Ia (CPT-1a) but decreasing expression levels of fatty acid synthase (FAS), which further contributed to a decrease in circulating TG levels. TT-treated mice displayed decreased SREBP2 mRNA levels and reduced blood TC levels. These findings strongly support that TT prevents diabetic and dyslipidemic states in STZ-induced diabetic mice evidenced by regulation of GLUT4, PPARα, FAS, and phosphorylation of AMPK.

AMPK-dependent modulation of hepatic lipid metabolism by nesfatin-1

The aim of this study was to characterize the mechanism by which peripheral nesfatin-1 regulates hepatic lipid metabolism. Continuous peripheral infusion of nesfatin-1 reduced adiposity and plasma levels of triglyceride and cholesterol. In mice fed high fat diet, peripheral nesfatin-1 significantly decreased hepatic steatosis measured by triglyceride content and oil red staining area and diameter. These alterations were associated with a significant reduction in lipogenesis-related transcriptional factors PPARγ and SREBP1, as well as rate-limited enzyme genes such as acaca, fasn, gpam, dgat1 and dgat2. In primary hepatocytes, nesfatin-1 inhibited both basal and oleic acid stimulated triglyceride accumulation, which was accompanied by a decrement in lipogenesis-related genes and an increase in β-oxidation-related genes. In cultured hepatocytes, nesfatin-1 increased levels of AMPK phosphorylation. Inhibition of AMPK by compound C blocked the reduction of triglyceride content elicited by nesfatin-1. Our studies demonstrate that nesfatin-1 attenuates lipid accumulation in hepatocytes by an AMPK-dependent mechanism.

The roles of IP3 receptor in energy metabolic pathways and reactive oxygen species homeostasis revealed by metabolomic and biochemical studies

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are calcium channels modulating important calcium-mediated processes. Recent studies implicate IP3R in cell metabolism, but specific evidence is missing regarding IP3R's effects on actual metabolic pathways and key energy metabolites. Here, we applied metabolomics and molecular biology to compare DT40 cell lines devoid of IP3R (KO) and its wild-type (WT) counterpart. NMR and LC–MS metabolomic data showed that the KO cell line has a very different basic energy metabolism from the WT cell line, showing enhanced Warburg effect. In particular, the KO cells exhibited significant perturbation in energy charge, reduced glutathione and NADPH ratios with slower cellular growth rate. Subsequent flow cytometry results showed that the KO cell line has a higher level of general reactive oxygen species (ROS) but has a lower level of peroxynitrites. This ROS disturbance could be explained by observing lower expression of superoxide dismutase 2 (SOD2) and unchanged expression of catalase. The higher ROS seems to be involved in the slower growth rate of the KO cells, with an ROS scavenger increasing their growth rate. However, the KO and WT cell lines did not show any noticeable differences in AMPK and phosphorylated AMPK levels, suggesting possible saturation of AMPK-mediated metabolic regulatory circuit in both cells. Overall, our study reveals IP3R's roles in ROS homeostasis and metabolic pathways as well as the effects of its KO on cellular phenotypes.

The antitumor effect of metformin with and without carboplatin on primary endometrioid endometrial carcinoma in vivo

ObjectivesNew treatment options for advanced and recurrent endometrial carcinoma (EC) are necessary. Epidemiological studies showed that diabetic patients using metformin have reduced risks of endometrial cancer (EC) incidence. Moreover, pre- and clinical studies demonstrated an antitumor effect by metformin, with and without additional treatments, for different solid malignancies. However, cancer cell-autonomous effects of metformin on EC have not been fully characterized yet. The aim of this study was to investigate the effect of metformin, with or without carboplatin, on patient-derived primary endometrioid EC cells xenografted in nude mice, to assess its ability to reduce or impair growth in already established tumors. MethodsTwo xenograft models were established by subcutaneous inoculation of primary endometrioid EC cell suspensions. Tumors were allowed to grow and then mice were treated with metformin (250mg/kg, daily, p.o.), carboplatin (50mg/kg, 1×/week, i.p.), or the combination of both compounds at the same concentration as single treatment, for three weeks. Effects of metformin treatment on the tumor mass were determined by tumor growth follow-up. Metformin influences on AMPK/mTOR cell signaling were evaluated by investigating AKT, AMPK and S6 phosphorylation levels. ResultsIn vivo, metformin did not affect the growth of EC tumors established from patient-derived primary cultures and the phosphorylation of AKT, AMPK and S6. In addition, no enhanced antitumor effect was determined by combining metformin and carboplatin treatments. ConclusionsMetformin, at clinically relevant concentrations, did not show effects on the growth of already established tumors. Adding metformin to carboplatin did not have synergistic effects.

Diet-induced obesity impairs hypothalamic glucose sensing but not glucose hypothalamic extracellular levels, as measured by microdialysis

Background/Objectives:Glucose from the diet may signal metabolic status to hypothalamic sites controlling energy homeostasis. Disruption of this mechanism may contribute to obesity but its relevance has not been established. The present experiments aimed at evaluating whether obesity induced by chronic high-fat intake affects the ability of hypothalamic glucose to control feeding. We hypothesized that glucose transport to the hypothalamus as well as glucose sensing and signaling could be impaired by high-fat feeding.Subjects/methods:Female Wistar rats were studied after 8 weeks on either control or high-lard diet. Daily food intake was measured after intracerebroventricular (i.c.v.) glucose. Glycemia and glucose content of medial hypothalamus microdialysates were measured in response to interperitoneal (i.p.) glucose or meal intake after an overnight fast. The effect of refeeding on whole hypothalamus levels of glucose transporter proteins (GLUT) 1, 2 and 4, AMPK and phosphorylated AMPK levels was determined by immunoblotting.Results:High-fat rats had higher body weight and fat content and serum leptin than control rats, but normal insulin levels and glucose tolerance. I.c.v. glucose inhibited food intake in control but failed to do so in high-fat rats. Either i.p. glucose or refeeding significantly increased glucose hypothalamic microdialysate levels in the control rats. These levels showed exacerbated increases in the high-fat rats. GLUT1 and 4 levels were not affected by refeeding. GLUT2 levels decreased and phosphor-AMPK levels increased in the high-fat rats but not in the controls.Conclusions:The findings suggest that, in the high-fat rats, a defective glucose sensing by decreased GLUT2 levels contributed to an inappropriate activation of AMPK after refeeding, despite increased extracellular glucose levels. These derangements were probably involved in the abolition of hypophagia in response to i.c.v. glucose. It is proposed that ‘glucose resistance' in central sites of feeding control may be relevant in the disturbances of energy homeostasis induced by high-fat feeding.